UC SANTA BARBARA (US) — The five personality traits considered universal to all humans may not be so universal after all, according to a study of an isolated indigenous group in Bolivia.

Anthropologists found that the Tsimane, who live in communities ranging from 30 to 500 people dispersed among approximately 90 villages, do not necessarily exhibit the five broad dimensions of personality—openness, conscientiousness, extraversion, agreeableness, and neuroticism.

While previous research has found strong support for what experts refer to as the “Big Five” in more developed countries and across some cultures, Michael Gurven, a professor of anthropology at the University of California, Santa Barbara, and his team discovered more evidence of a Tsimane “Big Two”—prosociality and industriousness.

These two traits combine elements of the traditional Big Five, and may represent unique aspects of highly social, subsistence societies.

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“Similar to the conscientiousness portion of the Big Five, several traits that bundle together among the Tsimane included efficiency, perseverance, and thoroughness,” says Gurven, who is also co-director of the Tsimane Health and Life History Project, a collaboration between UC Santa Barbara and the University of New Mexico, with co-director and co-author Hillard Kaplan. “These traits reflect the industriousness of a society of subsistence farmers.

“However,” Gurven says, “other industrious traits included being energetic, relaxed, and helpful. In small-scale societies, individuals have fewer choices for social or sexual partners, and limited domains of opportunity for cultural success and proficiency.

“This may require abilities that link aspects of different traits, resulting in a trait structure other than the Big Five.”

Since the mid-20th century, the Tsimane have come into greater contact with the modern world, although fertility and mortality rates remain high, the study notes. With formal education available to few Tsimane, the literacy rate is below 25 percent. Some 40 percent speak Spanish in addition to their native language.

They live in extended family clusters that share food and labor, and they usually limit contact with outsiders unless absolutely necessary, the authors said.

The researchers translated into the Tsimane language a standard questionnaire that assesses the Big Five personality traits, and interviewed 632 adults from 28 villages. Women comprised 48 percent of the sample, with an average age of 47 and little more than a year of formal education.

In addition, the researchers conducted a separate study to gauge the reliability of the self-report interviews by instead focusing on reports by peers.

For that study, they asked 430 Tsimane adults, including 66 people from the first study, to evaluate their spouse’s personality. The second study revealed that the subject’s personality as reported by his or her spouse also did not fit into a Big Five framework.

The researchers controlled for education level, Spanish fluency, gender, and age. Previous research has suggested that formal schooling and greater interaction with others, such as when villagers venture to markets in other towns, can lead to more abstract reflection and may be one reason why the Big Five replicates in most places, according to the authors.

However, there were no significant differences between the less educated, Tsimane-only speakers and the more educated bilingual participants.

While recent research on personality variation has demonstrated that the Big Five personality traits may be lacking in some developing cultures—particularly in Asia and Africa—Gurven notes that theirs is the first study of a large sample of an exclusively indigenous population completed with rigorous methodological controls.

He suggests that personality researchers expand beyond the limited scope of more Western, industrialized, and educated populations.

“The lifestyle and ecology typical of hunter-gatherers and horticulturalists are the crucible that shaped much of human psychology and behavior,” he notes. “Despite its popularity, there is no good theory that explains why the Big Five takes the form it does, or why it is so commonly observed.

“Rather than just point out a case study where the Big Five fails, our goal should be to better understand the factors that shape personality more generally.”